1. Field of the Invention
This invention relates to a SECAM color signal processing device for use in the SECAM color television system.
2. Description of the Related Art
On the transmitter side of a SECAM color television system, an (R-Y) signal and a (B-Y) signal are alternately superposed on two modulation carriers having different frequencies, each signal corresponding to one horizontal line, and are then transmitted to a receiver as a chroma signal. Hence, the chroma signal consists of a component fOR including the (R-Y) signal and a component fOB including the (B-Y) signal, each component corresponding to alternate lines.
On the receiver side, a 1H delay circuit (H=horizontal period) delays the chroma signal for one horizontal period, and synchronizes a signal component and a subsequent signal component. In other words, the component fOR including the (R-Y) signal and the component fOB including (B-Y) signal are synchronized. The components foR and foB are separately derived from the chroma signal by operating a line switch and supplied to (R-Y) and (B-Y) demodulators, respectively. The (R-Y) and (B-Y) demodulators demodulate these components and generate the demodulated (R-Y) and (B-Y) signals, respectively.
In the conventional SECAM color signal processing device described above, the chroma signal is input to the 1H delay circuit, and both a delayed signal and a non-delayed signal are obtained. The non-delayed signal is input to an input terminal of the line switch having two input terminals and two output terminals, and is output alternately from the two output terminals in every horizontal period. The delayed signal is input to the other input terminal, and is output also alternately from the two output terminals. As a result, the component fOR including the (R-Y) signal is output from only one of the output terminals, and the component fOB including the (B-Y) signal from the other.
As has been described above, the (R-Y) and (B-Y) signals are separated in the step of processing the high-frequency chroma signal. Hence, the two signals may interfere with each other near the line switch. When this interference occurs, the color of the image on the screen is degraded, and adjacent color regions of the image are not clearly distinguishable.